1. Field of the Invention
The present invention relates to the field of valve seats which are used to stem the flow of a fluid within a valve. More particularly, the present invention relates to an improved main valve seat for use in a fire hydrant having improved pressure loss characteristics at a given flow rate.
2. Description of the Prior Art
The typical valve seat configuration for a prior art fire hydrant is illustrated in FIG. 1. The hydrant 10 includes a vertical barrel 12 which extends upwardly from a connection with a contoured shoe 32, which is connected to a water supply pipe. A drain ring housing 20 is secured between the barrel 12 and the contoured shoe 32 by means of a bolt 26 and is sealed with respect to barrel 12 by a gasket 28. A bronze seat ring 22 is threadedly engaged to an interior portion of drain ring housing 20 through a threaded connection 24. The seat ring 22 has a beveled seating surface 23 defined in an interior portion thereof for sealing against a main valve element 36.
In such prior art valves, it was common to provide a first bevel 37 between the side surface 46 and top surface 44 of the main valve element 36. In operation, a valve stem 14 would be pulled up, causing a valve plate 34 to urge main valve element 36 toward seat ring 22, so that the first bevel 37 engaged the seating surface 23 of seat ring 22. However, when pressure was applied to the valve, it was common for plastic creep to occur, causing a bulge 38 to form in the recess defined between the seating surface 23 of seat ring 22 and valve plate 16. As a result, the material forming main valve element 36 would eventually become fatigued, causing the top surface of the valve element to deform and eventually break off. As a result, frequent maintenance of such devices was required.
It is clear that there exists a long and unfilled need in the prior art for a valve seat configuration which prevents pressure which is applied to the valve element from causing the top surface of the valve element to deform around its circumference and break off, as was the case with prior art valve members of this type.